In the prior art, plated IC lead frames are visually inspected for stains, flaws, glossiness, deformations, etc. in the final finishing stage. As the precision in such a visual inspection largely depending on the skill, experience, physical conditions and other human factors of individual inspectors and fluctuates widely, there has been much demand for an improvement. As remarkable progress was made in recent years in various optical devices, automatic performance of visual inspections became possible. One of the examples of these achievements was shown by the visual inspection system discussed in "Shoryoku to Jidoka (Laborsaving and Automation)", pp. 43-44, July, 1985; Ohm Publication House.
As electronic technology has been improved to a remarkable degree in recent years, the demand for ICs as well as for IC lead frames increased, which inevitably enhanced the significance of the efficiency of IC lead frame manufacture as well as that of inspection for plated IC lead frames at the final finishing stage.